Lucan's account of Caesar crossing the Rubicon (1.213–22) is dense with metapoetic allusion. Although the river has been specified as a small stream at Caesar's arrival (ut uentum est parui Rubiconis ad undas, 1.185), it becomes swollen, tumidus, as soon as Caesar ‘breaks the delay of war’ and ‘carries his standards in haste over the [now] swollen river’ (inde moras soluit belli tumidumque per amnem | signa tulit propere, 1.204-5). This has been pinpointed both as a metapoetic signpost of Lucan's engagement with the anti-Callimachean swollen river of grandiose epic (Callim. Hymn 2.108-9) at the outbreak of (his) Civil War,Footnote ¹ and as a programmatic statement that the whole Bellum Ciuile will set up a series of contrasts between Caesar's urgency in crossing boundaries and Lucan's narrative obstructions to or compliances with Caesar's progress.Footnote ² In fact, as Jamie Masters notes, ‘in spite of the “undoing of delay,” the perfect “tulit” and the adverb “propere,” Caesar has not crossed the river yet; or if he has, he must do it again’,Footnote ³ precisely at 1.213–22. Within this densely self-reflexive passage, Lucan inserts a palindromic acrostic which signals both the doubling of Caesar's action (or at least the poet's double mention of the action) and Lucan's poetic representation of Caesar taming the forces of nature.Footnote ⁴

In the ekphrasis of the Rubicon, Lucan seems to linger on those atmospherical phenomena which could have made Caesar's enterprise more risky. He first describes the state of the dark-red RubiconFootnote ⁵ in the summer, when it is made too hot by the burning season (cum feruida canduit aestas , 1.214), and then moves on to show how the winter season and three days of uninterrupted rain had actually provided the small stream with stronger and more dangerous waves (1.217-19), lines which may owe something to Livy's description of the river Druentia before Hannibal's Alpine crossing (Livy 21.31.10–12),Footnote ⁶ all the more so in view of Lucan's geographical incongruity of mentioning the Alps metonymically for ‘mountains’ at 1.219.Footnote ⁷

At the passage of Caesar's cavalry, however, the river seems to calm down and acquire a very moderate warmth:

Excepturus (221), in obliquum (220) and the polyptoton undis … undas … undas (213, 217, 222), perhaps reminiscent of a now famous Virgilian acrostic in the Eclogues,Footnote ⁸ may work as signals of the acrostic's presence.Footnote ⁹ Additionally, the meteorological notation in line 218 may also be reminiscent of Virgil's famous signature acrostic at G. 1.429-33, in its turn a probable allusion to an acrostic in Aratus’ Phaen. 783-87:Footnote ¹⁰ if so, the iunctura grauido … cornu (Luc. 218) can be seen to pinpoint the fact that reverse reading is also at play, since the Virgilian acrostic was also reversed, and similarly signalled and framed by the horns of the moon (obscuro … cornu, G. 1.428; obtunsis… cornibus, 1.433).Footnote ¹¹ If one ‘is ready to accept’ (excepturus, 221) the acrostic, to be read ‘obliquely’ (in obliquum, 220) and ‘palindromically’ between the lines, then the verb TEPET would ironically indicate that the Rubicon has actually acquired quite a moderate warmth at the crossing of Caesar's sonipes: not too hot, as in line 214, not too cold, as in lines 217–19.Footnote ¹² Secondly, the repetitive nature of the palindrome, to be read from top to bottom or – crossing back – from bottom to top, draws attention to Lucan's repetition of Caesar's crossing, and re-crossing, of the Rubicon.

In commenting on the scene, Roche interprets the danger posed to Caesar by the Rubicon in winter in line with Fantham's suggestion that ‘nature in BC may intermittently act with providential care for human safety’.Footnote ¹³ This may initially be true, but at the same time Caesar's crossing of the river, as with his cross of the Adriatic in the storm scene in Book 5,Footnote ¹⁴ suddenly turns the nature of Lucan's poem into a docile creature, subjugated to his own will. Yet, this transformation of nature is only put in motion by Lucan's own wish to comply with Caesar's actions. Ultimately, it is the poet who retains the privilege of turning the Rubicon and its waters from docile to swollen and then docile again (paruis … undis, 213; auxerat undas, 217; faciles … undas, 222), from hot to freezing, as if the river was an anti-Callimachean second Euphrates, and then moderately warm (TEPET), like the waters of the ‘speaking name’ Pisciatello, if that is indeed the river with which we should identify the Rubicon.Footnote ¹⁵ Thanks to Lucan's (mis)representation, Caesar can claim to have conquererd the stream (superato gurgite, 223) in the same ‘Hannibalic’ way that he had conquered the ‘Alps’ (superauerat Alpes, 182). Only now that the general's and the poet's intents have converged, can Caesar's war and Lucan's grandiose but Alexandrian epic properly begin.